MINISTRY OF EDUCATION AND TRAINING VIETNAM NATIONAL CHEMICAL GROUP

VIETNAM INSTITUTE OF INDUSTRIAL CHEMISTRY
--------------------------------------------

PHAM MINH TU

STUDY ON SYNTHESIS, CHACRACTERIZATION AND
EVALUATION OF PHOTOCATALYTIC ACTIVITY OF NANO
TIO2/(CNT, ZnO, SiO2)

Major: Theoretical Chemistry and Physical Chemistry
ID: 9.44.01.19

THESIS SUMMARY

HANOI -2019

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This thesis is completed in Viet Nam Institute of Industrial Chemistry

Advisors:
Prof. Vu Thi Thu Ha – Viet Nam Institute of Industrial Chemistry

Reviewer 1: Assoc. Prof. Dang Tuyet Phuong – Vietnam Academy of Science and
Technology

solution to the above problems. TiO2 is known as an ideal semiconductor for
photocatalysis as it is a non-toxic metal oxide with high photochemical
activity, low cost, chemical resistance, high refractive index, no
photochemical corrosion. At the same time, TiO2 catalysis happens under
normal temperature and pressure, post-reaction catalysts can be recovered
and reused easily. The products of the process are CO2, H2O or non-toxic
organic compounds. With these advantages, TiO2, especially nano TiO2, has
attracted the attention of scientists in the country and in the world.
However, for TiO2 catalysts, only ultraviolet radiations corresponding to
photons with energy greater than 3.2 eV (band gap energy of titanium
dioxide) are absorbed to produce photochemical effects. Therefore, only
ultraviolet radiation, which accounts for only about 4% of solar radiation, is
effective. In addition, the recombination of photogenerated holes and
photogenerated eletrons occurs very fast (from 10-12 to 10-9 seconds), which
is also a drawback when deploying photocatalytic systems on the basis of
TiO2. In order to solve the above problem, we need to produce nanosized
TiO2 with reasonable size and structure, and combine TiO2 with other
components to limit the possibility of recombination of photogenerated
holes and photogenerated eletrons and enhance photochemical activity in the
visible light region.
2. Objectives
The thesis is aimed at creating a catalyst material with high photocatalytic
activity which is simply synthesized from available raw materials. The new
kind of catalyst material is expected to meet the following requirements:
- High photocatalytic activity, effective treatment of pollutants;
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- Simple preparation, from available raw materials, low cost;
- Ability to work efficiently and stably in visible light region;

this catalyst has high sulfur selectivity, reaching 100% in the first 200
minutes of reaction;

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- The synthesis of catalyst system based on TiO2 sol/SiO2 by dip-coating
method has been systematically studied. The catalyst is highly active,
opening the direction for applying photochemical catalysis based on nanoTiO2 sol on the self-cleaning surface.
5. Thesis's structure
The thesis consists of 148 pages, divided into the following sections:
Introduction: 02 pages; Overview: 38 pages; Experimentation: 18 pages;
Results and Discussion: 77 pages; Conclusion: 02 pages; Innovations and
creativites: 1 page; List of projects that have been published: 01 page;
References: 9 pages (including 116 references). The thesis has 12 tables, 93
drawings and graphs.
B - MAIN CONTENTS OF THE THESIS
Chapter 1 - LITERATURE REVIEW
This section provides an overview of TiO2-based photochemical catalysis,
methods for synthesis of nanomaterials applied to photochemical catalysis
on the basis of TiO2 and denaturing substances, wastewater treatment
technologies which focus on wastewater in the laundry detergent industry.
Chapter 2: EXPERIMENTATION
The experimentation was carried out at National keylaboratory for
petrochemical and refining technologies
2.1. Synthesis of catalysts
a. Synthesis of TiO2 nanotubes
Two methods for systhesis of TiO2 nanotubes have been investigated
- TiO2 nanoparticles are synthesized from a number of different Ti sources
such as Ti(OC3H7)4, Ti(OC4H9)4, TiCl4; TiO2 nanotubes are synthesized

laundry detergent plant contains surfactants, typically linear alkyl sulfonate
(LAS) anionic surfactants, which have been pretreated by physical and
chemical methods, with COD in the range of 150-250 mg/l.
The organic matter content in wastewater before and after treatment is
analyzed by the total organic carbon (TOC) measurement.

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Chapter 3: RESULTS AND DISCUSSION
3.1. SYNTHESIS OF TIO2 NANOTUBES
3.1.1. Effects of raw materials

Ti(O-C3H7)4

Ti(O-C4H9)4

TiCl4

TiO2 thương mại

Fig 3.1. TEM images of TiO2 nanotubes which are fabricated from
different materials
Thus, through the study of effect of raw materials for the synthesis of TNTs.
The result showed that, the process of synthesizing TNTs from TiO 2
commercial is the simplest and cheapest. The products TiO2 get evenly size,
high quality equivalent to TiO2 nanotubes is obtained from other expensive
precursors or other method. So, TiO2 commercial is chose for the next
researchs.
3.1.2. Effect of conditions reaction



Fig 3.4. TEM images of TNT which are synthesized by different time
reaction: (a) 0h; (b) 1h; (c) 3h; (d) 5h và (e) 7h
3h is the reation time which is suited to concentration for synthesis process.

Fig 3.5. TEM images of TNTs before (a) and ater (b) treating by acid
The result showed that, the sample without treat by acid is almost inactive
photochemical whereas the sample treat by acid is high photochemical
activity. Thus, processing by axit impact significantly on photocatalytic
properties of TiO2 nanotubes.
3.1.3. Formation mechanism of TNTs
Dissolution of TiO2 precursor:
TiO2 + 2 NaOH → 2Na+ + TiO32- +H2O (1)
Dissolution–crystallisation of nanosheets
2Na+ + TiO32-→ [Na2TiO3] nanosheets (2)
Curving of nanosheets
2Na+ + TiO32-+ [Na2TiO3] nanosheets → [Na2TiO3] nanotubes (3)
Washing of nanotubes
[Na2TiO3] nanotubes + 2H2O → [H2TiO3] nanotubes +2 NaOH (4)

[TiO2] nanotubes
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3.2. SYNTHESIS OF PHOTOCATALYST BASED ON TiO2
NANOTUBES
3.2.1. Synthesis of catalysts MWCNTs/TNTs
Table 3.1. Specific area (SBET) of catalysts MWCNTs/ TNTs
Samples

Table 3.2. Band-gap values of the synthesized photocatalysts
(Kubelka-Munk model)
catalyst
Band gap (eV)
TNTs
3,26
1/10 MWCNTs/TNTs
3,21
1/1 MWCNTs/TNTs
3,08
2/1 MWCNTs/TNTs
3,05
MWCNTs
-

Fig 3.11. PL spectra of catalysts MWCNTs/TNTs

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3.2.2. Synthesis of TNTs/ZnO
6000

5000

Lin (Counts)

4000

3000


14

80


Fig 3.15. PL spectra of catalysts TNTs, TNTs/ZnO và ZnO
Table 3.3. Effect of ZnO content in nanocomposite TNTs/ZnO
STT

ZnO content in TNTs/ZnO

1
100
2
0
3
90
4
80
5
70
Shape the catalyst TNTs/ZnO

conversion MB after 30
min (%)
55
85
89
89


39,77

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Results of photocatalytic activity test in MB degradation reaction showed
that the catalysts has high activity photochemical with 95,3% to 97,2% in 50
min reaction.
3.2.3. Synthesis of TiO2/SiO2
The combination of TiO2 and SiO2 not only enhances TiO2 photochemical
activity, but also enhances the physical properties of the catalyst such as
Mechanical robustness, transparent.
a. Synthesis of sol silica

Fig 3.16. Partical size of sol silica: [Si]=0,4M, pH=8,
Temperature: 60oC

Fig 3.17. TEM image of sol silica when: (a) without surfactant, (b)
PEG 1000, (c) PVP K30
b. Synthesis of sol TiO2
Morphology and structure of partical in sol TiO2 are illustrated in fig. 3.18.

(a)

Sample C%TiO2=0,6%

(b) Sample C%TiO2=0,7%

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(stable)
Sol, transparent
Sol, transparent

Sol TiO2 which is synthesized at those suitable conditions, is evaluated
photocatalytic activity in photooxidation MB reaction under radiation solar,
the results were showed in fig. 3.59.
Độ chuyển hoá MB (%)

100
80
60
40
20
0
0

20
40
Thời gian phản ứng (phút)

60

80

Fig. 3.19. Photocatalytic activity of coating TiO2

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20

40 phản ứng
60 (phút)80
Thời gian

Fig 3.22. Photocatalytic activity of catalyst TiO2/SiO2
The results showed that, MB is almost degraded completely in 60 minutes.
That means, The results showed that, MB is almost degraded completely in
60 minutes. That means, SiO2 attendation in catalyst TiO2/SiO2 that
improved partly photocatalytic activity of catalyst.
The results are completely suitable with UV-Vis spectra of TiO2/SiO2 that
were illustrated in Fig. 3.23.

Hình 3.23. UV- Vis spectra of catalyst TiO2/SiO2
UV- Vis spectra of TiO2/SiO2 showed that the combination of TiO2 and SiO2
caused wide-open of absorb solar radiation which tend absorb of red
radiation.
3.2.4. Synthesis of sol TiO2-SiO2

Fig. 3.24. TEM images of sol: (a) sol SiO2, (b) sol TiO2, (c) sol SiO2TiO2

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Results of photocatalytic activity of SiO2-TiO2 test in MB degradation
reaction were illustrated in Fig. 3.25.
Độ chuyển hoá MB (%)

100

environment field.

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3.3.2. Investigation of photocatalytic activity of MWCNTs/TNTs 1/1 in
photooxidation H2S reaction.
The conversion and selectivity of H2S were recorded when it was test on
catalyst 1/1 MWCNTs/TNTs in oxidation H2S reaction . The results were
compared wiht catalyst TNTs. The comparison results were shown on fig.
2.27

Fig. 3.27. Convertion and selectivity of photooxydation H2S reaction
on catalyst 1/1 MWCNTs/TNTs and TNTs
The conversion of H2S and selectivity of sulfur were shown on fig. 3.28
and fig. 3.29.
100

Độ chuyển hoá H2S (%)

90
80

1/10
MWNTs/TNT

70
60
50
40


Fig. 3.29. Selectivity of sulfur

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Thus, catalyst MWCNTs/TNTs with ratio MWCNTs/TNTs = 1/1 were show
more stable performance than the others catalyst.
3.4. STUDY ON PHOTOCATALYTIC DEGRADATION OF MB BY
CATALYST TNTs/ZnO USING CONTINOUS-FLOW REACTION
SYSTEM
3.4.1. Effect of reaction time
The results were showed in fig.3.30. The conversion reached 100% when
flow-rate below 6.300 mL/h.

Fig. 3.30. Effect of flow-rate
3.4.2. Effect of temperature
The results showed that, the conversion wasn’t almost changed then
temperature changed from 20 to 40oC.

Fig. 3.31. Conversion of MB at different temperatures
3.4.3. Effect of pH
The results on Fig.3.32 showed that, the conversion reached max at pH=7.

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Fig. 3.32. Effect of pH value
3.4.4. Evaluate durability of catalyst
The result showed that, photocatalytic activity of catalyst was durability in

mg/l
mg/l

207
52,6

COD đầu ra, mg O/l

STT

100
80
60
40
20
0
5700

5800

5900

6000

6100

6200

6300


80
60
40
20
0
2

4

6

8

10

Giá trị pH

Fig. 3.37. Effect of pH to index COD of water

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Table 3.7. Specifications of water after treating
by photochemical process
No
Specifiactions
Results
2
TOC, mg/l
12,6